Fibreboards made of lignocellulose-containing fibres, in particular wood fibres, as such, as well as methods for manufacturing these ones are known by themselves from the state of the art, such that no reference has to be made to specifications at this point.
A medium density fibreboard, MDF board for short, is typically a board made of a wood fibre material. According to the relevant European norm the average raw density of a MDF board is comprised between 650 kg/m3 and 800 kg/m3. Boards having a medium raw density of more than 800 kg/m3 are designated as high density fibreboards (HDF) and those having a medium raw density of less than 650 kg/m3 are designated as light MDF. In case of a medium raw density of less than 550 kg/m3 one speaks of ultralight MDF.
Typically, medium density fibreboards and also ultralight MDF boards are manufactured by the so called dry process. According to this process, glued and dry fibres are produced by means of the so called blow line gluing, which fibres comprise a humidity content of less than 12% atro, wherein alternative gluing methods are known from the state of the art. Alternative gluing methods are for example the blender gluing and the dry fibre gluing. After a gluing of the fibres, another drying operation will be alternatively or optionally carried out. From the state of the art the use of so called multi-component fibres, for example bi-component fibres, is known. These are fibres with different glue components which can be for example activated by means of temperature.
The dry and glued or blended fibres will then be distributed for example by a spreader to form a mat. For this purpose, a transport belt will be typically used, onto which the spreader will scatter the fibres. In a last process step the formed mat will be pressed and the binding agent will harden by means of heat input. Usually this is carried out on continuously or discontinuously operating hot presses.
The board band manufactured in the above described manner can then be trimmed and cut to length as requested to form individual boards.
The above described procedure is sufficiently known from the state of the art.
GB 1 129 457 relates to laminated systems. GB 2 261 845 relates to a moulded part made of a mixture of resin and curing agent. US 2008/0197536 A1 discloses a moulded part made of wood fibres. These ones are generated from a dried pre-formed intermediate product. This specification does explicitly not disclose any information about the dimensioning with respect to the product height and the board thickness. No board is formed, but a dried mixture is directly introduced into a mould and cured there. DE 23 64 025 relates to mixtures of an elastomer and fibres for manufacturing moulded parts, wherein a pre-mixture is formed as fibreboard, i.e. an intermediate product. EP 0 004 999 relates to the manufacture of highly profiled moulded parts from pre-fabricated and slightly compressed fibreboards which are suitable for deep-drawing. EP 1 110 687 relates to the manufacture of light fibreboards. Deformations or other details are not disclosed here. DE 10153175 describes an installation for manufacturing boards from nonwovens, wherein a décor is manufactured in a compression moulding process for producing profiled tubular door skins. US 2013/0284357 discloses honeycomb panels and honeycomb systems. It discloses for example to cut a pre-fabricated corrugated plate into strips and to form honeycombs therefrom. It also discloses to cure masses which have been fabricated into undulated plates in moulds. This is a compression moulding process for moulded products. DE 43 42 789 discloses a method for manufacturing moulded parts from a sliding layer mat that can be hot pressed, which mat is generated by folding individual layers of fibre fleece on top of each other.
An improved procedure has been known from EP 1 110 687 B2. The here described method relates to the production of light fibreboards having an average raw density comprised between 60 and 350 kg/m3 which are used as heat insulating boards in the building sector. Herein, the particularity of the described method is the fact that a raw density profile is formed, wherein an increase of the raw density at the border of at least 20% with respect to the average raw density of the fibreboard is obtained. This is achieved procedurally in that the cover side of the mat will be sprinkled with water before a pressing operation. As a result a light fibreboard is obtained which comprises, with respect to its large surface, border areas, the density of which is higher by at least 20% than the average raw density. These border areas typically comprise a thickness comprised between 0.2 mm and 0.5 mm.
It is furthermore known to manufacture corresponding boards, in particular ultralight MDF boards in the form of sandwich boards. Herein external layers are made of a first fibre/binding agent mixture and intermediate areas are made of a second fibre/binding agent mixture. Thus, boards can be produced which are simplified with respect to their handling, treatment and further processing.
The known boards of most different types are used for very different purposes, mats as insulating materials, HDF boards for filling up, sheathing, covering and the like. The known mats and boards however comprise very different mechanical properties due to their different densities and production parameters. There is a need for as light boards as possible which are nevertheless extremely stable, but it has not been possible hitherto to cover this demand satisfactorily. Either the boards are mechanically highly resistant, for which they are usually provided with a massive raw density due to a high compression and thus they are heavy, or they are more lightweight and correspondingly less stable. It has been tried to find a remedy for this by combining materials. But there are limitations related to the process technology and the manufacturing machines.